Cooling device, electronic equipment device, and method of manufacturing cooling device

ABSTRACT

A compact, thin type and high cooling performance cooling device, an electronic apparatus and a method of manufacturing the same are provided. The cooling device ( 1 ) has a pair of a first substrate ( 2 ) and a second substrate ( 3 ) which are made of such a material having a low thermal diffusibility as glass, formed rectangular and bonded together via a silicon member ( 4 ). On bonding surfaces of these substrates ( 2 ) and ( 3 ), grooves ( 5 ) and ( 6 ) are formed. These grooves ( 5 ) and ( 6 ) are formed so as to function as a heat pipe of a loop type when these substrates ( 2 ) and ( 3 ) are bonded.

BACKGROUND OF THE INVENTION

The present invention relates to a cooling device for cooling heatgenerated by a driver for a card-type storage medium for use, forexample, in a personal computer, a digital camera and the like, and to amethod of manufacturing the same. The present invention also relates toelectronic apparatuses such as a personal computer, a digital camera,etc., incorporating this cooling device.

Since storage media such as Memory Stick (registered trade mark), SmartMedia (registered trade mark), Compact Flash (registered trade mark) arecompacter and thinner in size in comparison with conventional ones suchas a floppy disk and the like, and in addition, since a storage capacitythereof can be made enormous, it is becoming widely used in electronicapparatuses such as personal computers, digital cameras and the like.

This storage media include such a type which has a flash memory and adriver integral therewith and another type in which the driver isinstalled separately in the apparatus or in another card or the like. Inany case, its storage capacity is becoming considerably large.

By the way, with an increase in the capacity of the storage media alongwith such a trend of mass storage, a large amount of heat is generatedfrom the above mentioned driver, thereby causing a problem ofmalfunctioning or the like to occur.

Therefore, provision of a cooling device is considered, for example, ona side of the electronic apparatus, and as such a cooling method, atechnique using a heat pipe is referred to.

The heat pipe referred to here is made of a metal pipe having acapillary tube structure in an internal wall of the pipe, wherein theinside thereof is in vacuum and a small amount of water,Hydrochlorofluorocarbon or the like is sealed therein. When one end ofthe heat pipe is heated by making contact with a heat source, the liquidsealed therein is evaporated and vaporized to a gas, then as a latentheat (vaporization heat), the heat is absorbed. Then, it (vaporized gas)moves to a low temperature section at a high speed (almost at sonicspeed), in which it is cooled to return again to the liquid by releasingthe heat (latent heat discharge due to condensation). As the liquidreturns to its original place passing through the capillary tubestructure (or by gravity), it is possible continuously and efficientlyto transport the heat.

However, as the conventional heat pipe is of a tube type and becomesspatially a large-scaled device, it is not suitable as a cooling devicefor use in electronic apparatuses such as the personal computer, digitalcamera and the like for which a compacter and thinner size is demanded.

Thereby, in order to make the heat pipe compacter, a cooling device hasbeen proposed, wherein grooves are formed in each bonding surface of asilicon substrate and a glass substrate, and by bonding thesesubstrates, a flow channel for constituting a heat pipe is formedbetween these substrates. In addition, at the time of theabove-mentioned bonding thereof, a small amount of water orHydrochlorofluorocarbon or the like is sealed therein, which, byundergoing phase changes within the heat pipe, acts a role as the heatpipe.

However, if the heat pipe is constructed using the silicon substrate asdescribed above, because of a good heat conductivity of the siliconitself, heat from an object to be cooled is diffused well on the surfaceof the silicon, thereby causing a problem that evaporation of the liquidinside thereof becomes insufficient or does not evaporate at all, thusthe function as the heat pipe is not demonstrated sufficiently.

The present invention has been contemplated to solve the above-mentionedproblems associated with the conventional art, and an object thereof isto provide a cooling device of a compacter and thinner type as well aswith an improved cooling performance, electronic apparatuses using thesame and a method for manufacturing the same.

SUMMARY OF THE INVENTION

In order to accomplish the above-mentioned object, a cooling deviceaccording to a first aspect of a preferred embodiment of the presentinvention is characterized by comprising: a pair of a first and a secondsubstrates, which are made of a material having a lower thermalconductivity than silicon, each of which is disposed opposingly, andeach of which has grooves for constituting a heat pipe formed in eachopposing surfaces; and a bonding member interposed between the first andthe second substrates for bonding the first and the second substratessecurely.

According to the present invention, as the two substrates are bonded,and the grooves formed in their opposing surfaces constitute a flowchannel of the heat pipe, a compact and thin type becomes possible. Inaddition, as the material constituting the heat pipe has a lower thermalconductivity than silicon, the thermal diffusion can be prevented.Thereby, the cooling performance thereof is improved so that a functionas the heat pipe can be sufficiently achieved. Further, as the bondingof the two substrates is performed via the bonding member, it becomespossible to obtain a secured adhesion therebetween. That is, as amaterial of the substrates, if glass, plastics or the like that has alower thermal conductivity than silicon and is more applicable in termsof workability is used, adhesion between these substrates, however,becomes impaired. Therefore, according to the present invention, inorder to complement this drawback, the bonding member is interposedbetween these substrates. By way of example, as a combination of thematerials in this case, it may be arranged such that both the twosubstrates are glass, plastics, or either of which is glass and theother is plastic. Further, from a viewpoint of workability, economy orthe like, it is more preferable to use silicon, copper or the like asthe bonding member.

An electronic apparatus according to a second aspect of a preferredembodiment of the present invention is characterized by comprising: aslot capable of loading and unloading a card-type storage medium havinga flash memory therethrough; and a driver which is provided either on aside of the storage medium, on a side of the electronic apparatus, or ona portion separated from the apparatus, wherein in order to cool heatgenerated from the driver, the above-mentioned cooling device having theabove-mentioned structure is provided.

According to the present invention, because the cooling device havingthe above-mentioned structure, i.e. the compact and thinner sized, andfeaturing an improved cooling performance is installed, the electronicapparatus itself is rendered compacter and thinner, and also theoccurrence of malfunction or the like thereof is eliminated.

A method of manufacturing the cooling device according to a third aspectof the present invention is characterized by comprising: a step offorming grooves for constituting a heat pipe in each surface of a firstand a second substrates made of a material having a lower thermalconductivity than silicon; a step of forming a bonding member on asurface either of the first and the second substrates for securelybonding the first and the second substrates thereby; and a step ofbonding the surfaces of the first and the second substrates via thebonding member interposed therebetween.

According to the method of the present invention, it becomes possible tomanufacture the cooling device having the above-mentioned structureefficiently and reliably.

According to an aspect of an embodiment of the present invention, theabove-mentioned bonding step in the method of manufacturing theabove-mentioned cooling device is characterized by comprising an anodicbonding, ultrasonic bonding or thermal fusion bonding. By arranging asdescribed above, it becomes possible to bond efficiently and reliably.

According to an aspect of the embodiment of the present invention, inthe method of manufacturing the above-mentioned cooling device, the stepof forming the bonding member is characterized by comprising forming thebonding member by sputtering. According to the arrangement describedabove, it becomes possible uniformly to form a thin film withoutlimitation to materials. Thereby, at the time of assembling a heat pipeby bonding the substrates, it becomes possible to secure a reliableadhesion to be made therebetween due to non-existence of irregularitieson the bonding member.

According to an aspect of the preferred embodiment of the presentinvention, in the method of manufacturing the cooling device describedabove, the step of forming the grooves is characterized by comprisingforming the grooves by chemical etching or powder beam etching.According to such arrangement as described above, for example, by thechemical etching, or, in particular, in the powder etching, because fineparticles are used, it is enabled for them to reach even minute parts atthe time of forming the grooves. Thereby, because the grooves are formedaccurately, it is enabled to accomplish the function of the heat pipereliably.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing an exploded view of a coolingdevice according to the present invention;

FIG. 2 is a cross-sectional view showing the cooling device according tothe present invention in an assembled state;

FIG. 3 is a plan view showing a configuration of grooves formed in afirst glass substrate of the cooling device according to the presentinvention;

FIG. 4 is a plan view showing a configuration of grooves formed in asecond glass substrate of the cooling device according to the presentinvention;

FIG. 5 is a plan view showing an assembled state of the first and thesecond glass substrates of the cooling device according to the presentinvention;

FIGS. 6A to 6B are schematic diagrams for comparing thermal diffusionareas in respective substrates for use in a related art and the presentinvention;

FIG. 7 is a process flowchart showing a method of manufacturing thecooling device according to the present invention;

FIG. 8 is a schematic block diagram showing steps of forming grooves inthe cooling device according to the present invention;

FIG. 9 is a schematic diagram showing a powder beam etching apparatusused for forming the grooves of the cooling device according to thepresent invention;

FIG. 10 is a schematic diagram showing a DRIE apparatus used for formingthe grooves of the cooling device according to the present invention;

FIG. 11 is a schematic diagram showing an RIE apparatus used for formingthe grooves of the cooling device according to the present invention;

FIG. 12 is a schematic diagram showing a sputtering apparatus used forforming a thin film of the cooling device according to the presentinvention;

FIG. 13 is a schematic diagram showing an anodic bonding apparatus foruse in the bonding step of the cooling device according to the presentinvention;

FIG. 14 is a schematic diagram showing a chemical etching process foruse in the step of forming the grooves of the cooling device accordingto the present invention;

FIG. 15 is a diagram showing a process of manufacturing a cooling deviceaccording to another aspect of the preferred embodiment of the presentinvention;

FIG. 16 is a schematic diagram showing an ultrasonic bonding process ofthe cooling device according to still another aspect of the presentinvention; and

FIG. 17 is a schematic perspective view of a personal computerincorporating the cooling device according to the present invention.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

By referring to the accompanying drawings, preferred embodiments of thepresent invention will be described in the following.

[Cooling Device]

FIG. 1 is a perspective view of a cooling device according to thepresent invention in an exploded state, and FIG. 2 is a cross-sectionalview of the cooling device in an assembled state.

As shown in FIGS. 1 and 2, in a cooling device 1, a pair ofrectangular-shaped a first glass substrate 2 and a second glasssubstrate 3 made of, for example, Pyrex glass (registered trade mark))or Corning 7740 glass are bonded via a silicon member 4. On bondingsurfaces of these substrates 2, 3, grooves 5 and grooves 6 are formed.These grooves 5 and 6 are formed so as to function as a heat pipe in theshape of a loop when these substrates 5 and 6 are bonded.

As each of these substrates 5 and 6 is made of glass, it has a lowthermal diffusibility which is useful as the heat pipe. However, asadhesiveness of the bonding between these glass substrates 2 and 3 islow, a reliable bonding is secured by interposing the silicon member 4therebetween.

By referring to FIGS. 3 and 4, a structure of the grooves formed in eachsubstrate 2, 3 will be described in the following.

As to a cross-sectional structure of the grooves, although it isexplained in the description of FIG. 8 to be described later by way ofexample of a groove having a rectangular cross section, thecross-sectional structure of the groove according to the presentinvention is not limited thereto, and it may also have a cross-sectionin the shape of a triangle, semicircle, circle or the like.

As shown in FIG. 3, on a surface 2 a of the first glass substrate 2,there is formed the groove 5. A main part of this groove 5 is comprisedof a flow channel through which liquid and vapor flow, and a reservoirtank for supplying the liquid. More specifically, as the groove 5, thereis provided a flow channel 7 through which liquid such as water flowsand then the liquid is introduced from the flow channel 7 to a wick 8 tobe described later. The liquid introduced into the wick 8 is vaporizedto a gas therein, and is introduced into a gas receiving section 9. Thisgas is introduced into a radiator 11 via a flow channel 10 so as to becondensed and changed into the liquid, which then moves to a lowtemperature section 12. Further, it returns to the flow channel 7 again.As described above, a circulation between the liquid and gas takesplace.

In a reservoir 13 and a storage section 14, the liquid is stored. Theliquid in the reservoir 13 is caused to flow out when an amount of theliquid within the gas receiving section 9 becomes smaller than aprescribed amount. Further, the liquid in the storage section 14 iscaused to flow out when an amount of the liquid within the lowtemperature section 12 becomes smaller than a prescribed amount. Thatis, the reservoir 13 and the storage section 14 store the liquid inorder to prevent for the inside of the heat pipe from drying out, and itis arranged to supply the liquid into these reservoir 13 and the storagesection 14 when required.

Further, at a position in the center of the glass substrates 2, 3 and inthe vicinity of the flow channels 7 and 10, there is provided a thermalinsulation hole 15, whereby, it is ensured to prevent thermal diffusion.

As shown in FIG. 4, on a surface 3 b of the second substrate 3, thegroove 6 is formed. The groove 6 includes the wick 8, the radiator 11and a thermal insulation hole 16.

The wick 8 which functions as a cooling section vaporizes the liquidintroduced from the flow channel 7 and/or the reservoir 13, and flowsout the gas vaporized therein into the gas receiving section 9.

The radiator 11 condenses the gas introduced from the flow channel 10into a liquid and circulates it to the low temperature section 12.

By way of example, in this preferred embodiment of the presentinvention, each of the wick 8 and the radiator 11 is comprised of aplurality of fine grooves

Further, in a position opposite to the thermal insulation hole 15described above, there is provided the thermal insulation hole 16. Thesethermal insulation holes 15, 16 are provided as grooves on thesubstrates 2, 3 as means for preventing thermal diffusion.

FIG. 5 shows a state of the first glass substrate 2 and the second glasssubstrate 3 as bonded via the silicon member 4.

Inside a heat pipe constructed by bonding the first glass substrate 2and the second glass substrate 3 there is sealed a liquid. Then, theliquid sealed therein transfer the heat by changing its state from theliquid to the gas or from the gas to the liquid, thus circulating withinthe heat pipe, accordingly, functioning as the cooling device 1.

In the following, a mode of this circulation between the liquid and thegas will be described conveniently starting from the flow channel 7.

At first, the liquid flows from the flow channel 7 into the wick 8. Atthis time, if an amount of the liquid flowing into the wick 8 is below apredetermined amount, in order to avoid a dry-out, an amount of theliquid covering the shortfall is to be supplied from the reservoir 13.

The liquid flowed into the wick 8 is heated and boiled. A gas evaporatedby boiling is allowed to flow into the gas receiving section 9. This gasis caused to flow into the radiator 11 via the flow channel 10, where itis condensed to a liquid. The liquid thus condensed flows into the lowtemperature section 12 disposed below the radiator 11. This liquid isonce again circulated from the low temperature section 12 to the flowchannel 7. Further, in a case where the amount of the liquid flowed fromthe low temperature section 12 into the flow channel 7 is below apredetermined amount, the liquid stored in the liquid storage section 14is allowed to flow into the low temperature section 12.

By way of example, in the embodiment of the present invention, glass wasused as a material for the substrates. However, it is not limitedthereto, and other materials, for example, such as plastic may be used,or a combination of a glass substrate and a plastic substrate may beused as well. Further, any other material, provided that it has a lowerthermal conductivity than silicon, can be used as a material of thesubstrate.

FIGS. 6A to 6B are schematic diagrams showing heat diffusion areas onrespective substrates in a predetermined period of time, in which FIG.6A shows a case where silicon was used as the material of the substrate,and FIG. 6B shows a case where glass was used as the material of thesubstrate.

As shown in FIG. 6A, heat from a heat source A-1 (wick) on the siliconsubstrate diffuses broadly in directions as indicated by arrows in anarea (A-2). In contrast to this, heat from a heat source B-1 (wick) onthe glass substrates 2, 3 does not diffuse so broadly and diffuseswithin an area (B-2) as indicated by arrows.

In order to function as a heat pipe, heat greater than a predeterminedquantity must be concentrated in the wick. However, in the case wherethe material of the substrate is made of silicon as shown in FIG. 6A,its thermal diffusion becomes large such that its function cannot beattained sufficiently. In contrast thereto, in the case of the presentinvention, where the material of the substrate is made of glass orplastic as shown in FIG. 6B, its thermal diffusion is limited, that is,the heat is concentrated in the wick so that the function as the heatpipe is sufficiently accomplished.

[A Method of Manufacturing the Cooling Device]

FIG. 7 shows a process of manufacturing the cooling device.

Firstly, grooves for constituting a heat pipe are formed on thesubstrates 2, 3 (Step 701). On the surface 2 a of the first glasssubstrate 2 to be disposed on the bottom side, there are formed groovesfor use as a flow channel, a storage tank and the thermal insulationhole 15. Further, on the surface 3 b of the second glass substrate 3 tobe disposed on the upper side, there are formed grooves for use as thewick 8 having a function to effect a state change from liquid to gas,the radiator 11 having a function to effect a state change from gas toliquid, and a thermal insulation hole.

Next, a silicon thin film is formed as a bonding member on the surface 3b of the second glass substrate 3, for example, by sputtering (Step702). The glass substrate 2, 3, as they have a low thermaldiffusibility, can adequately demonstrate the function as the heat pipe,however, they have a drawback that it is not yet suitable theretobecause that the adhesiveness of bonding between these glass substrates2 and 3 is weak. Therefore, by forming the silicon thin film on thesurface 3 b of the second glass substrate 3, the adhesiveness isimproved. By way of example, a film thickness of the silicon thin filmis preferably approximately 200 to 500 nm. Further, of course, thesputtering may be performed on the surface of the first glass substrate2 as well.

Then, the first glass substrate 2 and the second glass substrate 3having the grooves formed thereon respectively are bonded via thesilicon thin film (Step 703). When mutually bonding the glass substrates2 and 3, a substance that undergoes state changes within the heat pipe,for example, water is sealed in the grooves.

FIG. 8 is a diagram for more specifically describing the steps offorming grooves in Step 701.

Firstly, the glass substrate 2, 3 is cleaned in a rinse solution or thelike (FIG. 8( a)).

On the surface of the glass substrate 2, 3 cleaned, a resist 17comprising an organic solvent, for example, “ORDYL” (product of TokyoOhka Kogyo Co., Ltd.) or the like is coated (FIG. 8( b)).

Then, a patterning formation is performed (FIG. 8 (c)). In thepatterning formation, at first, light exposure using a photo mask iscarried out to form a latent image of the mask pattern on the resist 17.The resist film is patterned by development.

Next, by blowing alumina powders of 50 to 60 μm onto the patterned glasssubstrate 2, 3, a powder beam etching as a first stage etching processis performed (FIG. 8 (d)). By this etching process, a groove 17 a havinga curved surface is formed.

Then, by performing a DRIE (Deep Reactive Ion Etching), RIE (ReactiveIon Etching) or limonene etching, a groove 17 b whose cross-section hasa right-angle is formed (FIG. 8( e)).

Hereinabove described is a series of processing for forming the grooveson the glass substrates 2, 3. In the following, more detaileddescription of each etching method will be made.

FIG. 9 is a diagram showing a constitution of a powder beam etchingapparatus 18 for performing the above-mentioned powder beam etchingprocess.

The glass substrate 2, 3 having patterning formed thereon is mounted ona movable carriage 18 a. In accompaniment with the movement of thecarriage 18 a to left and right directions, the glass substrate 2, 3disposed on the carriage 18 a is also moved to the left and rightdirections. Above the glass substrate 2, 3, there are disposed a numberof powder beam nozzles 18 b in a direction perpendicular to thedirection of the movement of the substrate by the carriage 18 a.

In accompaniment with the movement of the glass substrate 2, 3 to theleft and the right directions, alumina powders of approximately 50 to 60μm are blown against the glass substrate 2, 3. Thereby, the aluminapowders are ensured uniformly to be blown against the glass substrate 2,3. By the alumina powders blown against an exposed portion having nopatterning, the groove 17 a having a curved surface is formed.

FIG. 10 is a diagram showing a constitution of a DRIE apparatus forforming the groove 17 b whose cross-section has a right-angle from theabove-mentioned groove 17 a having the curved surface.

The DRIE apparatus 19 has a vacuum chamber 20 for accommodating thereinthe glass substrate 2, 3. In the upper direction in the vacuum chamber20, a helicon wave antenna 21 is disposed. Further, to the vacuumchamber 20, a vacuum pump 22 for depressurizing the air from the chamber20 is connected, and also a gas inlet port 23 for introducing a gas isprovided.

The glass substrate 2, 3 formed with the groove 17 a having the curvedsurface is mounted on a loading table 24 for the vacuum chamber 20.After loading the glass substrate 2, 3, inside the vacuum chamber 20 isdepressurized by the vacuum pump 22. After then, for example, a SF₆ gasis introduced into the vacuum chamber 20 from the gas inlet port 23.Further, a power supply 25 is turned on, a magnetic field is applied tothe vacuum chamber 20, and also a high frequency is applied to thehelicon wave antenna 21. By generating helicon waves inside the vacuumchamber 20, and by transporting energy from the helicon waves toelectrons through the process of Landau damping, electrons areaccelerated, then by colliding the electrons with gas molecules, a highionization rate is obtained. By use of plasma generated by a mutualinteraction between the helicon waves and electrons as described above,the etching process is carried out.

FIG. 11 is a diagram showing a constitution of the RIE apparatus forforming the groove 17 b whose cross-section has a right-angle from thegroove 17 a having the curved surface described above.

The RIE apparatus 26 has the vacuum chamber 20 for accommodating thereinthe glass substrate 2, 3. Inside the vacuum chamber 20, a pair of platetype electrodes 27 a and 27 b is disposed in parallel. Further, to thevacuum chamber 20, the vacuum pump 22 for depressurizing air within thechamber 20 is connected, and also the gas inlet port 23 for introducinga gas is provided.

The glass substrate 2, 3 formed with the groove 17 a having the curvedsurface is loaded on a lower electrode 27 b for the chamber 20. Afterloading the glass substrate 2, 3, the inside the vacuum chamber 20 isdepressurized by the vacuum pump 22. After then, for example, achlorinated gas or the like is introduced into the vacuum chamber 20 viathe gas inlet port 23. Simultaneously, when the power supply 25 isturned on, an upper electrode 27 a is applied with a voltage, and thelower electrode 27 b becomes the ground potential. Further, theintroduced chlorinated gas becomes a plasma state, and by acceleratingplasma ions generated therein, they are collided onto the glasssubstrate 2, 3. By using these plasma ions, etching process is carriedout.

By way of example, here, the introduced gas is referred to as thechlorinated gas, however, it is not limited thereto, and a gascontaining halogen compounds such as fluorine or the like may be used aswell.

FIG. 12 is a diagram showing a constitution of a sputtering apparatus 28for use in the above-mentioned processing.

The sputtering apparatus 28 is provided with a vacuum chamber 29, avacuum pump 30 for depressurizing inside the vacuum chamber 29, and agas inlet port 31 for introducing a gas.

In an upper portion inside the vacuum chamber 29, a substrate holder 32for firmly holding the glass substrate 2, 3 is disposed, and in a lowerportion opposing thereto, a target substrate 33 made of silicon isdisposed. Further, a voltage applying section (not shown) for applying avoltage across the glass substrate 2, 3 and the target substrate 33 isconnected.

Inside the vacuum chamber 29 is depressurized by the vacuum pump 30,and, for example, an argon gas is introduced into the vacuum chamber 29as an inert gas via the gas inlet port 31.

Because the argon gas is introduced into the vacuum chamber 29, when aDC high voltage is applied across the glass substrate 2, 3 and thetarget substrate 33 by means of the voltage applying section, the argongas is ionized. By causing the ionized argon gas to collide the targetsubstrate 33, an expelled target substance is formed as a film on theglass substrate 2, 3. Thereby, a silicon member 4 of the target materialis formed as a film on the glass substrate 2, 3.

By use of the sputtering method as described above, a thin film of thesilicon member 4 can be formed uniformly on the substrate withoutlimitation to the material of the substrate.

FIG. 13 is a diagram showing a schematic construction of an anodicbonding apparatus 34 for use in the bonding process described above.

The anodic bonding apparatus 34 is an apparatus for bonding two sheetsof glass substrates 2 and 3 via the silicon member 4 as the bondingmember.

The anodic bonding apparatus 34 is provided with a heater 35 for heatingthe whole of the anodic bonding apparatus 34, a lower electrode 36 a andan upper electrode 36 b disposed to interpose the glass substrates 2 and3 to be bonded therebetween, and a power supply 37 for supplying powerto these electrodes.

Using the heater 35, the anodic bonding apparatus 34 is heatedapproximately to 400° C. to 500° C. Further, by turning on the powersupply 37, a voltage is applied across the lower electrode 36 a and theupper electrode 36 b. Thereby, a large electrostatic attraction force isgenerated acting on an interface between the silicon member 4 and eachglass substrate 2, 3, thereby bonding them securely.

Further, according to the present invention, instead of theabove-mentioned powder beam etching, a chemical etching as shown in FIG.14 may be performed as well. A process of this chemical etchingprocessing will be described in the following.

In this chemical etching process, the glass substrate 2, 3 having thepatterning formed thereon (FIG. 14( a)) is introduced into an etchingbath 38 filled with, for example, nitric acid (FIG. 14( b)). Whereby,the nitric acid corrodes a portion where the pattern is not formed withthe resist, thereby performing the etching process (FIG. 14( c)).

As this etching process, likewise the above-mentioned powder beametching, is intended to form grooves having a curved surface by fineparticles, the above-mentioned second etching process is requiredafterward.

FIG. 15 shows a simple manufacturing process flow in a case where thematerial of the substrate 2, 3 is made of plastic.

On the surface of the substrate 2, a copper thin film 4 a is formed as abonding member (FIG. 15( a)).

Then, the substrate 2 and the substrate 3 are bonded in a state with thecopper thin film 4 a interposed therebetween (FIG. 15( b)). A bondingmethod thereof includes the following ultrasonic bonding or thermalfusion bonding.

FIG. 16 is a diagram for explaining a ultrasonic bonding process.

As shown in FIG. 16( a), on the surfaces of two sheets of plasticsubstrate 2 with a groove 17 b formed therein, a copper foil 4 a isformed by sputtering (FIG. 16( b)).

Then, the two sheets of the plastic substrates 2, 3 are stacked as shownin the drawing, pressed, and are subjected to ultrasonic vibration.Thereby, ultrasonic energy destroys an oxide film on the bondingsurface, as a result, activated copper atoms are allowed to bond withthe plastic substrate.

Further, instead of the ultrasonic bonding, this bonding can be carriedout by the thermal fusion bonding as well.

For example, two sheets of plastic substrates in a stacked state havingthe copper member interposed therebetween as the bonding member areheated. By application of this heating, the copper member interposedbetween these plastic substrates is melted to fuse with the plasticsubstrates.

By these methods also, these plastic substrates can be bonded via thecopper member securely.

[Electronic Apparatus]

FIG. 17 is a schematic, perspective view of a personal computerincorporating the cooling device according to the present invention.

A personal computer 39 has a slot 41 for allowing a card-type storagemedium 40 containing a flash memory and a driver 42 to be loaded andunloaded therethrough.

The cooling device 1 according to the present invention is disposed inthe personal computer 39 such that the wick thereof is positioned, forexample, immediately below the driver 42 of the storage medium 40 loadedtherein via the slot 41.

Although the electronic apparatus according to the present invention isdescribed here by way of example of a personal computer, it is notlimited thereto, and the cooling device according to the presentinvention may be installed in any other electronic apparatus such as adigital camera, video camera and the like as well.

As described heretofore, according to the present invention, the coolingdevice available in a compact and thin type and with an improved coolingperformance, the electronic apparatus incorporating the same, and themethod of manufacture thereof can be provided.

1. A cooling device comprising: a pair of first and second substrates,made of a material having a thermal conductivity lower than that ofsilicon, disposed in opposition to each other, and having a grooveformed in each opposing surface for constituting a closed loop heatpipe, said formed grooves being non-congruent to each other; and abonding member interposed between said first substrate and said secondsubstrate for bonding said first substrate and said second substrate. 2.A cooling device according to claim 1, characterized in that said firstand said second substrates are composed of glass or plastic.
 3. Acooling device according to claim 1, characterized in that said bondingmember is composed of silicon or copper.